The present invention relates to a light-emitting diode wherein a spherical lens is secured by adhesive to a semiconductor body having a luminescent zone therein with the shape of a spot. The luminescent zone is situated closer to one surface of the semiconductor body than an opposite surface thereof.
In optical communications technology, it is known to employ light-emitting semiconductor diodes, referred to as luminescent diodes (LED), in combination with glass fibers. Such a luminescent diode generally emits the radiation generated in it in all directions, or at least with an extremely large aperture angle. In order to be able to couple optimally high light power of the luminescent diode into a provided glass fiber, it is standard to provide the luminescent diode with a spherical lens for concentrating the radiation.
Such a luminescent diode has a semiconductor body. Under given conditions, this is formed of a substrate body and of one or more epitaxial layers applied to one of its surfaces. The actual light-emitting zone has the shape of a spot. The provided spherical lens, particularly a spherical lens, is applied to the semiconductor body or substrate body and is adjusted such that the focal point of the lens and this spot-shaped zone of the luminescent diode lie close to one another in known manner. A preferred technique for securing this spherical lens to the semiconductor body is the gluing of the lens. It is extremely involved, but necessary, to guarantee that the lens is situated in a central position relative to the zone forming the luminescent spot.
The employment of spheres as a lens for such luminescent diodes is known prior art. For example, see U.S. Pat. No. 4,501,637 incorporated herein and German No. A 32 32 526.
The figures of U.S. Pat. No. 4,501,637 show the sequence of the manufacturing method of a luminescent diode having a spherical lens situated thereon. Close to the one substrate surface the luminescent zone therein is prepared in the semiconductor substrate. A layer is then applied to the surface adjacent to this luminescent zone, a ring being produced by etching from this layer in adjustment relative to the luminescent zone. This ring serves for the acceptance or adjustment of the spherical lens. When applied and seated on this ring, it is then held at this ring and the substrate member with adhesive.
German No. A 32 32 526 discloses an integrated luminescent diode comprising a plurality of light-emitting regions in a shared substrate member. Each and every light-emitting region has a spherical lens allocated to it. The spacings of the light-emitting regions from one another are adapted to the diameter of the spherical lenses such that the distribution of the light-emitting regions in the substrate member and the spherical lenses applied to the substrate surface in the densest, planar sphere packing are arranged in adjusted fashion relative to one another. The individual spherical lenses thus abut tightly against one another. Adhesive with which the spherical lenses are held at the substrate member and relative to one another is situated in the clearances between these spheres. It is also provided in the arrangement of this publication that a depression adjusted relative to the individual light-emitting region is present on the substrate surface or in layers applied to the substrate surface, this depression potentially serving the purpose of adjusting the spherical lenses.
In the arrangement of this publication, the light-emitting regions lie close to that surface which carries the layers comprising the adjusting depressions. These depressions were to be previously employed in the method of manufacturing the light-emitting regions.
A frequently employed method for manufacturing a luminescent diode on which only a single spherical lens is situated (such as the luminescent diode of U.S. Pat. No. 4,501,637 but not that of German No. A 32 32 526) is the application of the spherical lens with manipulation thereof. For example, the correct position of the spherical lens is monitored by observation with the assistance of a magnifying glass. It must, therefore, also be incured that a lateral dislocation of the lens on the surface of the substrate member does not occur.